Magnetic recording type of photographic apparatus

ABSTRACT

A magnetic recording type of photographic apparatus comprises an iris for controlling the amount of light incident from a subject, an image sensor for converting a light signal obtained through the iris into an electrical signal, a converting circuit for converting a video signal supplied from the image sensor into a standard television signal, a motion-image signal processing circuit for applying signal processing to the standard television signal and forming a motion-image signal, a still-image signal processing circuit for applying signal processing to the standard television signal and forming a still-image signal, a recording circuit for recording the still-image signal in a still-image recording area of a video track formed obliquely with respect to a longitudinal axis of a magnetic tape, and for recording the motion-image signal in a motion-image recording area of the video track, an integrating circuit for integrating a video luminance signal supplied from the converting circuit, an arithmetic circuit for calculating a difference between the video luminance signal from the integrating circuit and a reference value, an iris controlling circuit for controlling the iris in accordance with the difference calculated by the arithmetic circuit, and a gain setting circuit for setting a gain of the arithmetic circuit to a higher gain when a still image is to be photographed than when a motion image is to be photographed.

This is a continuation application under 37 CFR 1.62 of priorapplication Ser. No. 08/274,107, filed Jul. 12, 1994, abandoned, whichis a continuation of Ser. No. 07/874,718, filed Apr. 27, 1992,abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording type ofphotographic apparatus capable of effecting motion-image recording andstill-image recording.

2. Description of the Related Art

In the field of magnetic recording, a demand for high-density recordinghas recently been increasing. To meet such a demand, there is provided,for example, a video tape recorder (VTR) of the type which is capable ofeffecting magnetic recording of high density by transporting a magnetictape at a reduced speed. However, a VTR provided with a fixed head forrecording an audio signal has the disadvantage that if an audio signalis recorded while simply transporting a magnetic tape at a reducedspeed, no large relative speed is obtained and the quality of reproducedsound is degraded. For this reason, a method has been adopted in whichthe length of each track scanned by a rotary head is extended withrespect to the track length used in the conventional art and an audiosignal which is compressed along its time axis is sequentially recordedin the additional portion of each extended track.

By way of example, such a method will be explained with reference to aVTR of the rotary 2-head helical scan type. As shown in FIG. 1, amagnetic tape 1 is wrapped around a rotary cylinder 2 through an angleof (180+θ) degrees or more and, as shown in FIG. 2, a video signalrecording area 5 and a PCM audio signal recording area 6 are traced by arotary head 3 or 4 during the rotation of the rotary cylinder 2 through180 degrees and during the rotation of the same through θ degrees,respectively. A PCM audio signal which is compressed along its time axisis recorded in the PCM audio signal recording area 6.

A method of recording a still image in a digital signal recording areahas been proposed as an applied example of the aforesaid method ofrecording a digital signal in one area while recording a video signal inanother area. Since the amount of information carried by a still imageis comparatively small, it is possible to record the entire still-imageinformation in the PCM audio signal recording area 6 on the magnetictape 1 by scanning a number of PCM audio signal recording areas 6.According to this method, not only is it possible to realize still-imagephotography utilizing a photographic apparatus and a recording mediumwhich are identical to those used for motion-image photography, but itis also possible to provide a high-quality still image. The quality ofthis still image is higher than that of a still image obtainable byrepeatedly reproducing a video signal from the same track on a magnetictape in a VTR while keeping the magnetic tape in a temporarily stoppedstate.

In such a magnetic recording type of photographic apparatus capable ofrecording a motion image and a still image, it is possible to performautomatic exposure control similar to that of a conventional camera formotion-image photography.

One example of automatic exposure control used in the conventionalcamera for motion-image photography will be described below withreference to FIG. 3. FIG. 3 shows an example of a camera formotion-image photography capable of performing automatic exposurecontrol based solely on an automatic iris control.

Light which has passed through an optical system 601 is conducted to anexposure adjustment mechanism (iris) 602, and the amount of the light isadjusted by the iris 602. The light is then made incident on an imagesensor 603 such as a CCD and is converted into an electrical signal bythe image sensor 603. The electrical signal from the image sensor 603 issubjected to processing such as gamma correction and separated into aluminance signal and a chrominance signal, by a camera signal processingcircuit 604. The luminance and chrominance signals are converted into astandardized television video signal which conforms to, for example, theNTSC system, by a camera encoder 605.

In the meantime, a luminance signal Y which has not been subjected togamma correction in the camera signal processing circuit 604 is suppliedto an integrator 606, where the luminance signal Y is subjected tointegration processing. An arithmetic device 607 calculates thedifference between the output of the integrator 606 and a referencevalue to generate a difference signal. The arithmetic device 607supplies the difference signal to a driver 609 as an exposure controlsignal. The driver 609 causes the actuator 610 to control the aperturesize of the iris 602 on the basis of the exposure control signal,thereby keeping constant the relationship between the output of theintegrator 606 and the predetermined reference value.

Another example of automatic exposure control used in the conventionalcamera for motion-image photography will be described below withreference to FIG. 4. FIG. 4 shows an example of a camera formotion-image photography capable of performing automatic exposurecontrol based on an automatic iris and automatic level control.

Light from a subject passes through a lens 702 and an iris 703 and ismade incident on an image sensor 704, where the incident light isconverted into an electrical signal. The iris 703 is controlled by theautomatic iris circuit 705 on the basis of the electrical signal fromthe image sensor 704. In the meantime, the signal from the image sensor704 is supplied to a voltage-controlled amplifier (VCA) 706, where thelevel of the signal is controlled. An automatic gain control (AGC)circuit which is a constituent element of the VCA 706 is controlled byan AGC control circuit 707 in accordance with the output of the VCA 706.A signal processing circuit 708 separates the output signal of the VCA706 into a chrominance signal and a luminance signal and performspredetermined processing to output a standard video signal (according tothe NTSC or PAL system).

Such a camera for motion-image photography is required to completeautomatic exposure control in a short time since the state of a subjectto be photographed varies temporally continuously during motion-imagephotography. However, if the speed of the automatic exposure control isexcessively fast, the amount of exposure may exceed a desired amountexposure or an exposure control operation may be repetitively performed.As a result, the photographed subject may be reproduced as a continuousimage of insufficient image quality. For this reason, it is desirablethat the automatic exposure control be performed with smoothness ratherthan at a high speed.

On the other hand, still-image photography is achieved by freezinginstantaneously the motion of a subject to be photographed. Accordingly,to prevent a shutter opportunity from being missed, high-speed automaticexposure and rapid control free from error are desired. As a result, ifautomatic exposure control similar to that used for the motion-imagephotography is performed during the still-image photography, no goodexposure is achieved.

In the magnetic recording type of photographic apparatus as shown inFIG. 1, it is possible to utilize AF control similar to that of amotion-image photographic apparatus. Since the state of a subject to bephotographed varies temporally continuously during motion-imagephotography, it is desired that the focusing time required for AF in themotion-image photographic apparatus be made short. However, if an objectother than a subject being photographed passes across the scene,excessively fast AF will respond to the object abnormally sensitively,and the photographed subject may be reproduced as a continuous image ofinsufficient image quality. For this reason, it is desirable to takeaccount of smoothness rather than high-speed response with respect tothe performance of AF.

A so-called hill climbing system is known as one automatic focusadjusting method to meet the above-described demand. In the hillclimbing system, a high-frequency component is extracted from a videosignal obtained from an image sensor and a photographic lens is movedfor focusing purpose until the level of the high-frequency componentreaches its maximum.

An automatic focus adjusting method utilizing the above-described hillclimbing system in the motion-image photographic apparatus shown in FIG.5 will be described below.

Light passes sequentially through an F lens 101 for focus adjustment, aV lens 102 for magnification variation, a C lens 103 for effectingcorrection to hold a focus plane, an iris 104 and an RR lens 105 forcorrectly focusing the light on an image sensing plane. The light isfocused on the image sensing plane of an image sensor 106 and convertedinto an electrical signal. The video signal outputted from the imagesensor 106 is amplified to a predetermined level by a preamplifier 107,and is then converted into a standard television signal throughpredetermined processing such as gamma correction, blanking processingand addition of a sync signal, by a camera signal processing circuit108.

The image sensor 106 is made to wobble along the optical axis to aslight extent in a predetermined cycle in synchronism with a timingsignal generated from a timing generating circuit 114, and the imagesensing plane is cyclically vibrated back and forth. A variation whichoccurs in the state of focus in accordance with the vibration is formedinto a modulating signal and the sensed-image signal is modulated.

The video signal from the preamplifier 107 is also supplied to aband-pass filter (BPF) 109, where a high-frequency component whichvaries with the state of focus is extracted from the video signal. Then,in a gate circuit 110, only a signal portion corresponding to a focusdetecting area (ranging frame) which is defined in a part of aviewfinder screen is extracted from the high-frequency component. Then,a peak value appearing during a frame period is detected by a peakdetecting circuit 111, and the detected peak value is envelope-detectedby a sync detecting circuit 112 in synchronism with a timing signalgenerated from the timing generating circuit 114. Since the image sensor106 is made to wobble back and forth along the optical axis as describedabove, signals AN, AF and AM are applied to the peak detecting circuit111 in response to the wobbling of the image sensor 106. The signals ANand AF appear on a near side and a far side, respectively, and are inreverse phase with each other, and the signal AM has an amplitude whichreaches a minimum at an in-focus point. The signals are sync-detected bythe sync detecting circuit 112 on the basis of the same frequency as thefrequency of the wobbling, and an output B is obtained as shown in FIG.6(b). As shown, the output B has a waveform whose signs on therespective near and far sides are reverse to each other and whichcrosses zero at the in-focus point.

FIG. 6(a) shows an output A obtained by plotting peak levels which aredetected by the peak detecting circuit 111 as a lens is moved between anear point and a far point through the in-focus point. FIG. 6(b) showsthe corresponding variation of the output B of the sync detectingcircuit 112. The output A exhibits a hill-shaped characteristic curvewhich reaches a maximum at the in-focus point and becomes smaller towardeach of the far and near sides.

The signal outputted from the sync detecting circuit 112 isappropriately amplified by an amplifier 113, and is then applied to afocusing-motor driving circuit 116. The focusing-motor driving circuit116 determines whether the state of focus is near focus or far focus,and the F lens 101 is driven to move up to an in-focus point at a speedaccording to the envelope detection output. Then, a specific loop gainis set for the output of the sync detecting circuit 112 by the amplifier113, and the focusing motor 117 is driven by the focusing-motor drivingcircuit 116 in accordance with the signal outputted from the amplifier113, whereby the focus of the F lens 101 is adjusted.

However, a number of problems take place if the above-describedautomatic focus adjusting system is applied to the above-describedmagnetic recording type of photographic apparatus capable of recording avideo signal in the recording area 5 and a digital still image signal inthe recording area 6. For example, during still-image photography, itmay take a long time to focus a subject to be photographed, or sincehunting occurs during focusing, the subject may not be frozeninstantaneously. As a result, a shutter opportunity will be missed.

The still-image photography in the above-described apparatus is achievedby freezing instantaneously a subject to be photographed. Accordingly,to prevent a shutter opportunity from being missed, a high-speedmagnification varying operation is required and it is desired that anin-focus position be rapidly reached without error.

On the other hand, during the motion-image photography, the state of asubject to be photographed varies temporally continuously and it is,therefore, desired to reduce the time required to reach a target pointduring magnification adjustment. However, excessively fast adjustmentmay lead to the problem of exceeding the position of a desired focallength and hence the adjustment operation may be repetitively performed.As a result, the photographed subject may be reproduced as a continuousimage of insufficient image quality. For this reason, it is desirable totake account of smoothness rather than high-speed response with respectto the performance of the magnification varying operation.

As is apparent from the above description, still-image photography andmotion-image photography differ from each other with regard to therequired nature of the magnification varying operation. If an identicalmagnification varying operation is carried out during each of thestill-image photography and the motion-image photography, the problemthat no appropriate adjustment of focal length is achieved will alsotake place.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to solve theproblem that if still-image photography and motion-image photography areto be implemented by means of a single photographic arrangement, desiredoperational characteristics differ for the respective still-image andmotion-image photographic modes, and to provide a photographic apparatuscapable of optimumly effecting not only still-image photography but alsomotion-image photography by means of a single photographic arrangement.

To achieve the above object as well as optimum control over the amountof exposure, according to a first aspect of the present invention, thereis provided a magnetic recording type of photographic apparatus whichcomprises an iris for controlling the amount of light incident from asubject, image sensing means for converting a light signal obtainedthrough the iris into an electrical signal, converting means forconverting a video signal supplied from the image sensing means into astandard television signal, motion-image signal processing means forapplying signal processing to the standard television signal provided bythe converting means and forming a motion-image signal, still-imagesignal processing means for applying signal processing to the standardtelevision signal provided by the converting means and forming astill-image signal, recording means for recording the still-image signalsupplied from the still-image signal processing means in a still-imagerecording area of a video track formed obliquely with respect to alongitudinal axis of a magnetic tape, and for recording the motion-imagesignal supplied from the motion-image signal processing means in amotion-image recording area of the video track, integrating means forintegrating a video luminance signal supplied from the converting means,arithmetic means for calculating a difference between the videoluminance signal from the integrating means and a reference value, iriscontrolling means for controlling the iris in accordance with thedifference calculated by the arithmetic means, and gain setting meansfor setting a gain of the arithmetic means to a higher gain when a stillimage is to be photographed than when a motion image is to bephotographed.

To achieve the above object as well as the optimum control over theamount of exposure, according to a second aspect of the presentinvention, there is provided a magnetic recording type of photographicapparatus which comprises an iris for controlling the amount of lightincident from a subject, image sensing means for converting a lightsignal obtained through the iris into an electrical signal, convertingmeans for converting a video signal supplied from the image sensingmeans into a standard television signal, motion-image signal processingmeans for applying signal processing to the standard television signalprovided by the converting means and forming a motion-image signal,still-image signal processing means for applying signal processing tothe standard television signal provided by the converting means andforming a still-image signal, recording means for recording thestill-image signal supplied from the still-image signal processing meansin a still-image recording area of a video track formed obliquely withrespect to a longitudinal axis of a magnetic tape, and for recording themotion-image signal supplied from the motion-image signal processingmeans in a motion-image recording area of the video track, automaticiris controlling means for automatically controlling the iris inaccordance with a level of the video signal supplied from the imagesensing means, automatic level controlling means for automaticallycontrolling a level of a video signal supplied from the image sensingmeans but not converted into the standard television signal, and gainsetting means for setting a gain of the automatic level controllingmeans to a higher gain when a still image is to be photographed thanwhen a motion image is to be photographed.

In the first aspect of the present invention, the gain setting meanssets the gain of the arithmetic means to a higher gain when a stillimage is to be photographed than when a motion image is to bephotographed, and a video luminance signal from the converting means isintegrated by the integrating means. The arithmetic means calculates thedifference between the video luminance signal supplied from theintegrating means and the reference value, and the iris controllingmeans controls the iris in accordance with the difference calculated bythe arithmetic means.

In the second aspect of the present invention, the automatic iriscontrolling means automatically controls the iris in accordance with thelevel of the video signal supplied from the image sensing means, thegain setting means sets the gain of the automatic level controllingmeans to a higher gain when a still image is to be photographed thanwhen a motion image is to be photographed, and the automatic levelcontrolling means automatically controls the level of the video signalsupplied from the image sensing means but not converted into thestandard television signal.

To achieve the above object as well as optimum AF control, in accordancewith a third aspect of the present invention, there is provided amagnetic recording type of photographic apparatus which comprises animage sensor, converting means for converting a video signal suppliedfrom the image sensor into a standard television signal, motion-imagesignal processing means for applying signal processing to the standardtelevision signal provided by the converting means and forming amotion-image signal, still-image signal processing means for applyingsignal processing to the standard television signal provided by theconverting means and forming a still-image signal, recording means forrecording the still-image signal supplied from the still-image signalprocessing means in a still-image recording area of a video track formedobliquely with respect to a longitudinal axis of a magnetic tape, andfor recording the motion-image signal supplied from the motion-imagesignal processing means in a motion-image recording area of the videotrack, wobbling means for causing the image sensor to wobble along anoptical axis, controlling means for making a wobbling frequency of thewobbling means higher by a predetermined frequency for still-imagephotography than for motion-image photography, extracting means forextracting a high-frequency component of the video signal supplied fromthe image sensor which is being made to wobble by the wobbling means,peak detecting means for detecting a peak during a frame period of thehigh-frequency component extracted by the extracting means, detectingmeans for detecting a deviation from an in-focus point on the basis ofthe peak detected by the peak detecting means, and driving means fordriving a focusing lens on the basis of the deviation detected by thedetecting means.

In the third aspect of the present invention, the controlling meansmakes the wobbling frequency of the wobbling means higher by apredetermined frequency for still-image photography than formotion-image photography, and the wobbling means causes the image sensorto wobble along the optical axis thereof. The extracting means extractsa high-frequency component of the video signal supplied from the imagesensor which is being made to wobble by the wobbling means, and the peakdetecting means detects a peak during the frame period of thehigh-frequency component extracted by the extracting means. Thedetecting means detects a deviation from an in-focus point on the basisof the peak detected by the peak detecting means, and the driving meansdrives a focusing lens on the basis of the deviation detected by thedetecting means.

Further, to achieve the above-described object as well as to enable bothan optimum magnification varying operation and optimum adjustment offocal length, in accordance with a fourth aspect of the presentinvention, there is provided a magnetic recording type of photographicapparatus which comprises an image sensor, converting means forconverting a video signal supplied from the image sensor into a standardtelevision signal, motion-image signal processing means for applyingsignal processing to the standard television signal provided by theconverting means and forming a motion-image signal, still-image signalprocessing means for applying signal processing to the standardtelevision signal provided by the converting means and forming astill-image signal, recording means for recording the still-image signalsupplied from the still-image signal processing means in a still-imagerecording area of a video track formed obliquely with respect to alongitudinal axis of a magnetic tape, and for recording the motion-imagesignal supplied from the motion-image signal processing means in amotion-image recording area of the video track, focal length adjustingmeans for adjusting a focal length, and driving controlling means fordriving the focal length adjusting means with smoothness duringmotion-image photography and at a high speed during still-imagephotography.

In the fourth aspect of the present invention, the focal lengthadjusting means for adjusting a focal length is driven with smoothnessduring motion-image photography and at a high speed during still-imagephotography, by the driving controlling means.

The above and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionof preferred embodiments of the present invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a magnetic-tape transport system in aVTR for recording or reproducing a video signal and an audio signal;

FIG. 2 is a schematic view showing recording tracks formed on a magnetictape by the head shown in FIG. 1;

FIG. 3 is a schematic block diagram showing one example of an automaticexposure control device for a conventional camera for motion-imagephotography;

FIG. 4 is a schematic block diagram showing another example of theautomatic exposure control device for the conventional camera formotion-image photography;

FIG. 5 is a schematic block diagram showing the construction of amotion-image photographic apparatus;

FIGS. 6(a) and 6(b) are explanatory views which serve to illustrate anautomatic focus adjusting method adopted in the motion-imagephotographic apparatus shown in FIG. 5;

FIG. 7 is a schematic block diagram showing a first embodiment of thepresent invention;

FIG. 8 is a schematic block diagram showing a second embodiment of thepresent invention;

FIG. 9 is a flowchart showing a control procedure followed by a controlcircuit 16 in the second embodiment;

FIG. 10 is a schematic block diagram showing a third embodiment of thepresent invention;

FIG. 11 is a schematic block diagram showing a fourth embodiment of thepresent invention;

FIG. 12 is a schematic block diagram showing a fifth embodiment of thepresent invention;

FIG. 13 is a flowchart showing a control procedure followed by theimage-sensor driving means shown in FIG. 12;

FIG. 14 is a schematic block diagram showing a sixth embodiment of thepresent invention;

FIG. 15 is a schematic block diagram showing a seventh embodiment of thepresent invention; and

FIG. 16 is a flowchart showing the operation of the seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowin detail with reference to the accompanying drawings.

FIG. 7 shows a first embodiment of the present invention.

The arrangement shown in FIG. 7 includes constituent elements 601 to 610which are substantially identical to those described above in connectionwith FIG. 3. The arrangement further includes an A/D conversion circuit11 for performing A/D conversion of a signal supplied from the cameraencoder 605, a rate conversion circuit 12 for allocating a digitalsignal supplied from the A/D conversion circuit 11 to the respective PCMareas of a plurality of tracks, a PCM conversion circuit 13 forperforming PCM conversion of a signal supplied from the rate conversioncircuit 12, a recording circuit 14 for selectively recording a videosignal supplied from the camera encoder 605 and a still-image signalsupplied from the PCM conversion circuit 13, an SV/MV mode selectingswitch 15 for selecting either one of a still-image recording mode (SVmode) and a motion-image recording mode (MV mode), and a control circuit16. If the SV mode is set through the SV/MV mode selecting switch 15,the control circuit 16 sets the gain of the arithmetic device 607 to ahigh level with respect to the MV mode. Further, the control circuit 16controls the recording circuit 14 in accordance with a photographic modeset through the SV/MV mode selecting switch 15.

The operation of the arrangement shown in FIG. 7 will be describedbelow.

If the MV mode is selected through the SV/MV mode selecting switch 15,the control circuit 16 sets the gain of the arithmetic device 607 to alevel which is the same as that of the gain set in the conventional art.If the SV mode is selected, the control circuit 16 sets the gain of thearithmetic device 607 to a level which is higher than that of the gainset in the MV mode.

Light which has passed through the optical system 601 is conducted tothe iris 602, and the amount of the light is adjusted by the iris 602.The light is then made incident on the image sensor 603 such as a CCDand is converted into an electrical signal by the image sensor 603. Theelectrical signal from the image sensor 603 is subjected to processingsuch as gamma correction and separated into a luminance signal and achrominance signal, by the camera signal processing circuit 604. Theluminance and chrominance signals are converted into a standardizedtelevision video signal which conforms to, for example, the NTSC system,by the camera encoder 605.

In the case of the MV mode, the video signal from the camera encoder 605is recorded in the respective motion-image recording areas of particularvideo tracks by the recording circuit 14. In the case of the SV mode,the video signal from the camera encoder 605 is subjected to A/Dconversion by the A/D conversion circuit 11, and the digital signal fromthe A/D conversion circuit 11 is subjected to conversion which isperformed by the rate conversion circuit 12 for the purpose ofallocating the digital signal to the respective PCM areas of a pluralityof tracks. The signal from the rate conversion circuit 12 is subjectedto PCM conversion by the PCM conversion circuit 13, and is then recordedin the respective still-image recording areas of particular video tracksby the recording circuit 14.

In the meantime, a luminance signal Y which has not been subjected togamma correction in the camera signal processing circuit 604 is suppliedto the integrator 606, where the luminance signal Y is subjected tointegration processing. The arithmetic device 607 calculates thedifference between the output of the integrator 606 and a referencevalue, and then supplies the resultant difference signal to the driver609 as an exposure control signal. The driver 609 causes the actuator610 to control the aperture size of the iris 602 on the basis of theexposure control signal, thereby keeping constant the relationshipbetween the output of the integrator 606 and the predetermined referencevalue.

FIG. 8 shows a second embodiment of the present invention. Thearrangement shown in FIG. 8 is provided with an SV release button 17 inaddition to the constituent elements of the first embodiment. A controlprocedure which is followed by the control circuit 16 is shown in FIG.9.

If it is determined in Step S11 that the SV release button 17 has beenpressed halfway, the process proceeds to Step S12, where a high-speedexposure correcting operation for still-image photography is enabled. Ifit is determined in Step S13 that the SV release button 17 has beenfully pressed, the video signal is subjected to A/D conversion, rateconversion and PCM conversion in that order. The thus-obtained stillimage is recorded in Step S14.

FIG. 10 shows a third embodiment of the present invention.

The arrangement shown in FIG. 10 includes constituent elements 702 to708 which are substantially identical to those described above inconnection with FIG. 4. The arrangement further includes an A/Dconversion circuit 41 for performing A/D conversion of a signal suppliedfrom the signal processing circuit 708, a rate conversion circuit 42 forallocating a digital signal supplied from the A/D conversion circuit 41to the respective PCM areas of a plurality of tracks, a PCM conversioncircuit 43 for performing PCM conversion of a signal supplied from therate conversion circuit 42, a recording circuit 44 for recording a videosignal supplied from the signal processing circuit 708 and a still-imagesignal supplied from the PCM conversion circuit 43, and a controlcircuit 45. The control circuit 45 causes the AGC control circuit 707 tocontrol the gain of the AGC circuit of the VCA 706, in accordance with aphotographic mode which is set through the SV/MV mode selecting switch15. Further, the control circuit 45 controls the recording circuit 44 inaccordance with the photographic mode set through the SV/MV modeselecting switch 15.

The operation of the arrangement shown in FIG. 10 will be describedbelow.

If the MV mode is selected through the SV/MV mode selecting switch 15,the gain of the AGC circuit of the VCA 706 is set to a level which isthe same as that of the gain set in the conventional art. If the SV modeis selected, the gain of the AGC circuit of the VCA 706 is set to alevel which is higher than that of the gain set in the MV mode.

Light from a subject passes through the optical system 702 and the iris703 and is made incident on the image sensor 704, where the incidentlight is converted into an electrical signal. The electrical signal fromthe image sensor 704 is supplied to the voltage-controlled amplifier(VCA) 706, where the level of the electrical signal is controlled. TheAGC circuit which is a constituent element of the VCA 706 is controlledby the AGC control circuit 707 in accordance with the output of the VCA706. The signal processing circuit 708 separates the output signal ofthe VCA 706 into a chrominance signal and a luminance signal andperforms predetermined processing to output a standard video signal(according to the NTSC or PAL system).

In the case of the MV mode, the standard video signal from the signalprocessing circuit 708 is recorded in the respective motion-imagerecording areas of particular video tracks by the recording circuit 44.In the case of the SV mode, the video signal from the signal processingcircuit 708 is subjected to A/D conversion by the A/D conversion circuit41, and the digital signal from the A/D conversion circuit 41 issubjected to conversion which is performed by the rate conversioncircuit 12 for the purpose of allocating the digital signal to therespective PCM areas of a plurality of tracks. The signal from the rateconversion circuit 42 is subjected to PCM conversion by the PCMconversion circuit 43, and is then recorded in the respectivestill-image recording areas of particular video tracks by the recordingcircuit 44.

If the photographic mode selected through the SV/MV mode selectingswitch 15 is the MV mode, the gain of the AGC circuit which isassociated with exposure correction is set to a low level, so that theAGC circuit provides an output so as to vary the amount of exposure on astep-by-step basis until the amount of correct exposure is reached.Accordingly, a smooth exposure correction operation can be performed.

If the photographic mode selected through the SV/MV mode selectingswitch 15 is the SV mode, the gain of the AGC circuit which isassociated with exposure correction is set to a high level, so that theAGC circuit provides an output so as to vary instantaneously the amountof exposure to the amount of correct exposure. Accordingly, a high-speedexposure correction operation is achieved.

FIG. 11 shows a fourth embodiment of the present invention. Thearrangement shown in FIG. 11 is provided with the SV release button 17in addition to the constituent elements of the third embodiment. Acontrol procedure which is followed by the control circuit 45 isessentially the same as that shown in FIG. 9, and the descriptionthereof is omitted.

As is apparent from the above description, in accordance with any of thefirst to fourth embodiments which are respectively arranged in theabove-described manners, it is possible to achieve the advantage thatoptimum exposure control can be performed.

A fifth embodiment of the present invention will be described below.

The arrangement shown in FIG. 12 includes constituent elements 101 to114, 116 and 117 which are substantially identical to those describedabove in connection with FIG. 5. The arrangement further includes avideo signal processing circuit 115 for processing a standard videosignal supplied from the camera signal processing circuit 108 to form amotion-image signal.

The still-image signal forming circuit of the shown arrangement consistsof an A/D conversion circuit 118, a rate conversion circuit 119 and aPCM conversion circuit 120. The A/D conversion circuit 118 converts intoa digital signal a standard television signal supplied from the camerasignal processing circuit 108. The rate conversion circuit 119 performsconversion for allocating the digital signal to the respective PCM areasof a plurality of tracks. The PCM conversion circuit 120 performs PCMconversion of the signal supplied from the rate conversion circuit 119.

The shown arrangement further includes a recording circuit 121 forrecording a still image or a motion image, an SV/MV mode selectingswitch 123 for switching each of the video signal processing circuit 115and the A/D conversion circuit 118 between the SV mode (still-imagerecording mode) and the MV mode (motion-image recording mode), arecording switch 124 for switching the recording circuit 121 between theSV mode and the MV mode, and image-sensor driving means 125 using apiezoelectric element. The image-sensor driving means 125 varies thefrequency at which the image sensor 106 wobbles along the optical axis,in accordance with a mode selected by the SV/MV mode selecting switch123, thereby causing the image sensor 106 to wobble toward a near-focusside or a far-focus side for the purpose of optical-path modulation.

FIG. 13 is a flowchart showing a control procedure which is followed bythe image-sensor driving means 125.

In Step S111, it is determined whether the photographic mode is the SVmode or the MV mode. If the result is the SV mode, the process proceedsto Step S112, where AF control for still-image photography, which isbased on a closed loop having a high loop gain, is executed. In StepS114, it is determined whether the recording switch 124 is on or off. Ifit is determined that the recording switch 24 is not on, the processreturns to Step S111. If it is determined that the recording switch 124is on, still-image photography is performed in Step S115.

If it is determined in Step S111 that the MV mode has been selected, theprocess proceeds to Step S113, where AF control for motion-imagephotography is performed.

Then, in Step S114, it is determined whether the recording switch 124 ison. If it is determined that the recording switch 124 is not on, theprocess returns to Step S111. If it is determined that the recordingswitch 124 is on, motion-image photography is performed in Step S115.

If the amount of wobbling of the image sensor 106, that is, the signalamplitude thereof, is increased in the SV mode, the amplitude of anoptical-path modulation signal component in a sensed-image signaloutputted from the image sensor 106 becomes large. Accordingly, theclosed-loop gain of a focus control system is increased which consistsof the image sensor 106, a signal processing system such as a band-passfilter or a sync detecting circuit 112 for extracting the optical-pathmodulation signal component from the sensed-image signal, an amplifier113, a focusing-motor driving circuit 116 and a focusing motor 117. Byincreasing the closed-loop gain of such a focus control system,detection sensitivity relative to the amount of defocus is increased andhence the output level of the sync detecting circuit 112 is increased.In consequence, the focusing motor 117 is driven at a speed higher thanits normal driving speed so that a high-speed AF operation can beperformed. In addition, the detection sensitivity relative to the amountof defocus is increased and hence the accuracy of detection of a finefocus position in the neighborhood of an in-focus position is improved.Accordingly, high-speed and high-precision AF control suitable forstill-image photography can be achieved.

In the above-described case, a signal indicative of the SV mode isoutputted from the SV/MV mode selecting switch 123, and a standardtelevision signal is subjected to predetermined conversion processing ineach of the A/D conversion circuit 118, the rate conversion circuit 119and the PCM conversion circuit 120. The resultant signal is inputted tothe recording circuit 121, and the still image is recorded by therecording circuit 121 in accordance with the output of the recordingswitch 124.

If the mode selected through the SV/MV mode selecting switch 123 is theMV mode, the signal from the camera signal processing circuit 108 isprocessed by the video signal processing circuit 115. The signal fromthe video signal processing circuit 115 is inputted to the recordingcircuit 121, and the motion image is recorded by the recording circuit121 in accordance with the output of the recording switch 124.

The above-described method of detecting a high-frequency component froma video signal to drive a focusing lens toward an in-focus point may beimplemented not only by utilizing the wobbling of the image sensor butalso by causing the focusing lens or a magnification varying lens towobble along the optical axis. Accordingly, the method utilizing onlythe wobbling of the image sensor is not construed as limiting the scopeof the present invention. To the contrary, the present invention isintended to encompass other similar methods such as the method ofcausing the focusing lens or the magnification varying lens to wobblealong the optical axis.

As is apparent from the above description, in accordance with the fifthembodiment which is arranged in the above-described manner, it ispossible to achieve the advantage that AF control for motion-imagephotography can be optimumly performed and also the advantage that AFcontrol for still-image photography can be optimumly performed at ahigher speed.

A sixth embodiment of the present invention will be described below.

The arrangement shown in FIG. 6 includes a photographic lens system 201provided with a focusing lens 201a for focus adjustment and a zoominglens 201b for magnification variation, an iris 202 for controlling theamount of light passed through the photographic lens system 201, asolid-state image sensor 203 for photoelectrically converting a subjectimage formed in its image sensing plane to a sensed-image signal, asample-and-hold circuit (S/H) 204 for sampling and holding a signal fromthe solid-state image sensor 203, and a camera signal processing circuit205 for converting a signal supplied from the S/H 204 into apredetermined television signal.

The shown arrangement also includes a video signal processing circuit206 for processing a video signal supplied from the camera signalprocessing circuit 205, an A/D conversion circuit 207 for performing A/Dconversion of a signal supplied from the camera signal processingcircuit 205, a rate conversion circuit 208 for performing conversion forallocating a digital signal supplied from the A/D conversion circuit 207to the respective PCM areas of a plurality of tracks, a PCM conversioncircuit 209 for performing PCM conversion of a signal supplied from therate conversion circuit 208, and a recording circuit 210 for selectivelyrecording a video signal supplied from the video signal processingcircuit 206 and a still-image signal supplied from the PCM conversioncircuit 209.

The shown arrangement also includes a zooming button 211 for selectingeither one of zooming toward a telephoto side (T) and zooming toward awide-angle side (W), an SV/MV mode selecting switch 212 for selectingeither one of the still-image recording mode (SV mode) and themotion-image recording mode (MV mode), a motor 215 such as a steppingmotor for driving the zooming lens 201b, a zooming driver 214 fordriving the motor 215, and a control circuit 213. In the case of the SVmode, the control circuit 213 causes the zooming driver 214 to controlthe motor 215 so that it runs at a high speed, in accordance with aselection output from the zooming button 211. In the case of the MVmode, the control circuit 213 causes the zooming driver 214 to controlthe motor 215 so that it runs smoothly, in accordance with the selectionoutput.

The operation of the sixth embodiment will be described below.

If the control circuit 213 detects that the photographic mode is the SVmode or the MV mode, a still image is recorded in the respectivestill-image recording areas in particular video tracks or a motion imagein the respective motion-image recording areas in the particular videotracks, by the recording circuit 210 in accordance with the detectedphotographic mode. The motor 215 is driven by the zooming driver 214 inaccordance with the output of the zooming button 211 which indicateswhether zooming toward the telephoto side or zooming toward thewide-angle side has been selected, so that the lens 201b is actuated toeffect a magnification varying operation conforming to the selectionoutput of the zooming button 211. Further, the gain of the associatedcircuit is controlled by the control circuit 213 in accordance with theselected photographic mode. If the SV mode is selected, the gain isincreased with respect to the output of the zooming button 211, whereasif the MV mode is selected, the gain is decreased with respect to thatof the zooming button 211. Accordingly, in the case of the SV mode, themotor 215 is driven to run at a high speed so that a high-speedmagnification varying operation is performed. In the case of the MVmode, the motor 215 is driven to run smoothly so that a smoothmagnification varying operation is performed.

FIG. 15 shows a seventh embodiment of the present invention. Thearrangement shown in FIG. 15 is provided with an SV release button 221in addition to the constituent elements of the sixth embodiment. FIG. 16is a flowchart showing a control procedure which is followed by thecontrol circuit 222.

Referring to the flowchart of FIG. 16, if it is determined in Step S211that the SV release button 221 has been pressed halfway, the processproceeds to Step S212, where a magnification varying operation forstill-image photography is enabled. If it is determined in Step S213that the SV release button 221 has been fully pressed, the obtainedstill image is recorded in Step S214.

If the SV release button 221 is released and the selection of astill-image photographic mode is detected by the control circuit 222, amagnification varying operation during the release operation isperformed at a high speed by the control circuit 222.

As is apparent from the above description, in accordance with each ofthe sixth and seventh embodiments which are respectively arranged in theabove-described manners, it is possible to optimumly perform amagnification varying operation and adjustment of a focal length duringeither motion-image photography or still-image photography.

What is claimed is:
 1. An image sensing apparatus comprising:(a) imagesensing means for photoelectrically converting an image light incidentfrom a subject; (b) gain control means for controlling a signal gain ofan output of said image sensing means; (c) mode specifying means forselectively specifying a still-image photographic mode and amotion-image photographic mode; and (d) speed control means forincreasing gain control speed of said gain control means when saidstill-image photographic mode is specified by said mode specifyingmeans.
 2. An image sensing apparatus according to claim 1, wherein saidimage sensing means includes a charge-coupled device.
 3. An imagesensing apparatus according to claim 1, wherein the controlcharacteristic includes an amplification degree.
 4. An image sensingapparatus, comprising:(a) image sensing means for obtaining an imagesignal; (b) gain control means for controlling a signal gain of anoutput of said image sensing means; (c) signal processing means forperforming signal processing to an output signal of the gain controlmeans; (d) mode specifying means for specifying a still-imagephotographic mode and a motion-image photographic mode; and (e) speedcontrol means for increasing gain control speed of said gain controlmeans when said still-image photographic mode is specified by said modespecifying means.
 5. An apparatus according to claim 4, wherein saidimage sensing means includes a charge-coupled device.
 6. An apparatusaccording to claim 4, wherein the signal processing means includes meansfor forming a motion-image signal and a still-image signal from theoutput of the gain control means, and wherein recording means recordsthe still-image signal in a still-image recording area of a video trackformed obliquely with respect to a longitudinal axis of a magnetic tape,and records the motion-image signal in a motion-image recording area ofthe video track, the still-image recording area and the motion-imagerecording area being formed adjacent to each other on a single videotrack.